1. Field of the Invention
The invention relates to thermal imaging systems and, more particularly, to a microcomputer based microbolometer array uncooled focal plane array sensor.
2. Discussion of the Related Art
Thermal imaging systems are useful for a number of low light level applications such as night vision, and for imaging during conditions of reduced visibility, or for thermal image viewing for purposes of process or conditioning monitoring in industrial or residential environments. These imagers generally produce a two dimensional real time display for the operator to view. The real time images allow the user to view objects and/or scenery under conditions where the human eye would not normally function or to see thermal signatures of objects.
Some focal plane array sensors operate using an image intensifier tube or cryogenically cooled sensor. Image intensifier tubes amplify existing visible and near visible light having wavelengths in the range of 0.4 microns to 1.0 micron. Such an image intensifier sensor has several limitations. Because image intensifier sensors amplify existing light, they cannot work in total darkness. They also experience washout when there are sudden flashes of light or high ambient lighting. Such sensors are unable to detect signals through obstacles such as camouflage or smoke. Further, image intensifier tubes do not perform hot spot detection which is an important function for some imaging applications.
Other conventional imaging systems amplify visible and near infrared radiation at night to create images. This type of radiation amplification is typically accomplished with photomultiplier tubes. A photomultiplier tube amplifies light having a wavelength in the range of, for example, 0.4 microns to 1.0 micron, using micro-channel devices. Available microchannel devices are self contained with a photosensitive input surface on one side and an output display surface on the other. No cooling is required.
Other thermal vision devices utilize two dimensional infrared focal plane arrays such as PtSi, Ins and HgCdTe operating at cryogenic temperatures. Unfortunately, these focal planes require complicated cooling systems.
Other focal plane arrays such as pyroelectric arrays and ferroelectric arrays are also used for night vision devices. These devices utilize focal plane arrays that are AC coupled and require mechanical scanners or choppers to create infrared images. Because such focal plane arrays do not require complicated cooling systems they are typically referred to as xe2x80x9cuncooledxe2x80x9d focal plane arrays. Unfortunately they are heavy have reduced sensitivity and consume an undesirable amount of power in comparison to other sensors and to the uncooled sensor of the present invention.
In order to overcome drawbacks associated with conventional apparatus it is, therefore, desirable to have a self-contained, low cost, low power consumption light weight, portable thermal sensor that collects scene radiation in the visible to infrared range, outputs digital image data and creates a real time visible display. It is also desirable to have a sensor wherein images are created with the use of a microbolometer focal plane array having a digital image data output integrated into a single chip, processing electronics, power supply and display.
The present invention provides a staring focal plane array sensor comprising optics located along an optical path, for transmitting radiation. A focal plane array and integrated circuit, located along the optical path for receiving the transmitted radiation, responsively produces image signals from the transmitted radiation. The integrated circuit includes means for converting the image signals into digital image data at digital image data outputs.
In one aspect of the invention, the present invention provides an uncooled focal plane array sensor comprising a microbolometer focal plane array integrated into a semiconductor circuit with a digital image output in a package of modular construction having smaller size, lighter weight, and lower power consumption than prior art devices. The uncooled focal plane array may be tailored to operate in the 8 to 14 micron wavelength region on naturally occurring scene radiation Since it does not need visible light, it can operate in total darkness where image intensifiers cannot. It can also operate during the daytime without wash out. The focal plane array of the invention does not require cooling of a continuous mechanical chopper.
Other objects, features and advantages of the present invention will become apparent to those skilled in the art through the description of the preferred embodiment, claims and drawings herein wherein like numerals refer to like elements.